Treatment of respiratory depression with 2 - hydroxy - 2,6,6 - trimethylcyclohexylidene acetic acid,2-lactone or 2-hydroxy-2,6,6 - trimethylcyclohexyl acetic acid,gamma-lactone



E. c. TOMPKINS 3,501,574

ON WITH 2-HYDROXY-2 ,6,6, ACETIC ACID. 2-LACTONE OR 2-HYDROXY-2,6,6-TRIMETHYLCYCLOHEXYL March 17, 1970 TREATMENT OF RESPIRATORY DEPRESSI TRIMETHYLCYCLOHEXYLIDENE ACETIC ACID, 'n-LACTONE Filed April 17, 1968 TETBAHQDQORCTIUIDIOLIDE DI HI'DQOACTHJIDIOLIDE -BE.ME.6E|DE.

PE UTILEUETETEA'ZOLE oeue DOSE. LEVEL.

WWWJOQWwN mzkumuum no mmmvlaz TETBAHQDQOACTINIDIOU DE E m L w m m m m a m A A 2 o T 2 M E O T q u M m \W\\ '8 N E A a E m E 6 4 M I 5:2 II 5 0 m w m u O m u o 8 7 6 5 M 5 Z w 0 DOSE IN 1.0 5s

arousal and return to consciousness.

United States Patent 3,501,574 TREATMENT OF RESPIRATORY DEPRESSION WITH 2 HYDROXY 2,6,6 TRIMETHYL- CYCLOHEXYLIDENE ACETIC ACID, Z-LAC- TONE OR 2-HYDROXY-2,6,6 TRIMETHYL- CYCLOHEXYL ACETIC ACID, 'y-LACTONE Edward Crosby Tompkins, Winston-Salem, N.C., assignor to R. J. Reynolds Tobacco Company, Winston-Salem, N.C., a corporation of New Jersey Filed Apr. 17, 1968, Ser. No. 722,080

Patented Mar. 17, 1970 Schumacher, Ser. No. 701,104, filed Jan. 29, 1968. Hydrogen-ation of dihydroactinidiolide results in the formation of tetrahydroactinidiolide. The following illustrates the synthesis of the analeptic agents of this invention.

SYNTHESIS OF DIHYDROACTINIDIOLIDE A solution of 300 grams of ,B-ionone (92% purity) in 45-00 milliliters of absolute ethanol is irradiated using a quartz filter and a ZOO-watt Hanovia mercury vapor quartz lamp. The B-ionone-ethanol solution is constantly stirred and kept at 55-60 C. with the aid of an oil bath (9095 C.) throughout the irradiation. The amount of oxide formed in the reaction is determined every 24 hours by gas chromatography. Equilibrium is reached after 72 hours. The solvent is removed under reduced pressure to give approximately 300 grams of irradiation product which is fractionated on a helix-packed column x 1.5 centimeters) at 17 millimeters mercury pressure as shown below:

DISTILLA'IION OF IRRADIATION PRODUCT The invention relates to the treatment of respiratory depression in mammals.

Analeptic agents or analeptics are stimulants which counteract depression of the central nervous system due to drug-induced coma. Such analeptic agents are thus useful in the management of poisoning with barbiturate and non-barbiturate sedatives and hypnotics. The analeptics are administered to stimulate respiration thus causing The present invention involves the discovery that the 40 compounds 2 hydroxy 2,6,6 trimethylcyclohexylidene acetic acid, 'y-lactone (also known as dihydroactinidiolide) and 2-hydroxy-2,6,6-trimethylcyclohexyl acetic acid, 'y-lactone (also known as tetrahydroactinidiolide) counteract respiratory depression and are thus useful as analeptics. The process of the present invention comprises administering to a mammalian host experiencing respiratory depression a pharmacologically effective dose of dihydroactinidiolide or tetrahydroactinidiolide. Of the two compounds, tetrahydroactinidiolide is more effective as a respiratory analeptic and is the preferred analeptic.

Dihydroactinidiolide and tetrahydroactinidiolide are administered to a mammalian host experiencing respiratory depression parenterally. Dihydroactinidiolide is generally administered in doses of about 1.5 milligrams to 150 milligrams per kilogram of host body weight and tetrahydroactinidiolide is generally administered in doses of about 0.5 milligram to 150 milligrams per kilogram of host body weight.

The analeptic agents of this invention can be represented by the following formulae:

Twenty grams of 6,7,8,8a-tetrahydro-2,5,5,Sa-tetramethyl5H-l-benzopyran is dissolved in 80 milliliters of benzene and the resulting solution aerated with compressed air at 70-80 C. The oxidation is continued for three days. Removal of the solvent followed by distillation and crystallization gives pure dihydroactinidiolide in approximately 30% yield.

SYNTHESIS OF TERTAHYDROACTINIDIOLE Ten and five-tenths grams of dihydroactinidiolide is dissolved in 50 milliliters of acetic acid and placed in a Parr hydrogenation bottle along with a catalytic amount of platinum oxide. A pressure of 50 pounds is applied and the hydrogenation allowed to proceed for 18 hours. The reaction mixture is filtered, diluted with 100 milliliters of water, and extracted with five 30-milliliter portions of hexane. The hexane extracts are combined, washed with 5% sodium carbonate solution and with water, dried over anhydrous sodium sulfate, and concentrated. The residue, 10 grams, is crystallized from a pentane-ether solution and recrystallized twice from the same solvent to provide approximaately 7.1 grams of pure tetrahydroactinidiolide having a melting point of 7880 C.

The analeptic activity of dihydroactinidiolide and tetrahydroactinidiolide is evident from the following animal test data in which the new analeptic agents of the invention were compared with two known presently marked analeptic agents, namely gemegride and pentylenetetrazole.

The experimental animals used were mice. Twenty-four hour intraperitoneal (1P) LD s in normal animals (non- I H OH H 3 3 a depressed animals) were determined for the four analeptics tested. The intraperitoneal LD dose, i.e. the dose 2 causing death in 50% of these animals, was as follows:

0 O Mg./kg.

\O \Ofi Dihydroactinidiolide 15 C 3 3 Tetrahydroactinidiolide 10 Dihydroactinidiolide Tetrehydroactinidiolide Bemegnde Dihydroactinidiolide can be synthesized by the method Pentylenetetrazole disclosed in the copending application of Joseph N.

The intraperitoneal dose of pentobarbital necessary to '3 kill 99% of the mice within one hour after administration was found to be 150 milligrams per kilogram.

Mice were given an intraperitoneal LD dose of pentobarbital and four minutes later a dose of analeptic equivalent to 1, 2, 4, 6, 8, 10 or 12 times the LD was administered intraperitoneally. There were ten male and ten female mice in each drug-dose combination. Thus, there were seven dilferent levels per drug at twenty mice per level making a total of 140 mice per drug. Ten male and ten female control mice received 0.5 cubic centimeter of saline four minutes after the LD injection of pentobarbital. When necessary the pentobarbital, bemegride and pentylenetetrazole were diluted to the proper stock with distilled water. Dihydroactinidiolide and tetrahydroactinidiolide were dissolved in 10% propylene glycol.

The results of the experiments were analyzed by the analysis of variance method. Drug, dose, and sex were all fixed eifects, so main eifects and the two-factor interaction were tested against the error term by means of the F test. The three-factor interaction was used as the error term. The Newman-Keuls sequential range test was used to detect statistically significant diiferences between treatment means.

The number of dead mice was recorded at 24 hours after drug administration and the results are graphically summarized in FIGURE I.

As seen from FIGURE I, at 24 hours after administration dihydroactinidiolide was superior to bemegride and pentylenetetrazole with respect to the total number of mice saved and tetrahydroactinidiolide protected a significantly (P .Ol) larger number of mice than the other three respiratory stimulants. For the mice receiving tetrahydroactinidiolide, the survival rate never dropped below 55% over the range from 4 to 12LD while with the other analeptics, the survival rate exceeded the 5% mark in only two incidences; 60% of the mice receiving the 2LD dose of bemegride survived, and 65% survived at the 4LD dose of dihydroactinidiolide.

The respiratory stimulating ability in mammals of the analeptic agent employed in accordance with this invention is further illustrated by tests on guinea pigs poisoned with pentobarbital. Various dose levels of dihydroactinidiolide and tetrahydroactinidiolide and the known analeptic agents, bemegride and pentylenetetrazole, were administered to guinea pigs. The dose levels of each analeptic agent administered were as follows:

Dose level (mg/kg.)

Four replications of guinea pigs were employed and within each replication each of the six dose levels of analeptics (8 in the case of tetrahydroactinidiolide) of the four drugs was injected into one male and one female animal. One male and one female guinea pig serving as controls received one cubic centimeter of physiological saline. Thus, there were 54 animals per replication and a total of 216 animals. The guinea pigs were secured to an animal board and 0.2 cubic centimeter of 2% lidocaine was administered subcutaneously into each foreleg. Cut downs were then made to expose the accessory cephalic vein. A cannula attached to a syringe containing pentobarbital, 16 milligrams per cubic centimeter, was inserted into one vein and a cannula connected to a syringe containing the analeptic was inserted into the vein on the 0pposite foreleg. An automatic syringe was used to infuse the pentobarbital at the rate of 0.5 cubic centimeter per minute. Respiration and electrocardiogram were monitored with an E and M physiograph. The pentobarbital gradually depressed respiration until apnea occurred. Fifteen seconds after the last breath the automatic syringe was turned oif and 20 seconds after the last breath the analeptic was injected. The solutions of analeptics were prepared so that 1 cubic centimeter would contain the desired amount of compound and this was administered over an approximately five second period. The subsequent effect on respiration was recorded and any electrocardiogram abnormalities or convulsions were recorded.

A restoration of a normal respiratory pattern of at least 30 seconds duration was considered a positive response. This end point was chosen because once a normal respiratory pattern of this duration is established, it is possible to keep the animal alive by additional injection of low doses of the analeptic. However, in the large majority of cases, respiration continued for several minutes and many of the animals survived.

The results from the experiment were analyzed by the analysis of variance method. The combining of the results from the six levels within each sex and drug cell was necessitated by the all or none type nature of the data. Drug and sex effects were fixed while the replication effect was random. Thus, the two factor interactions and main eifect for replication were tested against the three factor interaction. The main eifect for sex was tested against the sexxreplication interaction and the main eifect for drug was tested against the drugXreplication interaction. The F test was employed for these comparisons and the Newman-Keuls sequential range test was used to compare differences between treatment means.

Two separate analyses of the data were performed. One was based on the data which included all eight levels of tetrahydroactinidiolide and the other was from the data based on only the six lowest levels of tetrahydroactinidiolide. The graph of FIGURE II depicts the results when the data is summarized over batch and sex, thus giving a clear representation of events at each dose level.

From the data plotted in FIGURE II the range and effectiveness of the analeptic agents of this invention are readily apparent. As can be seen, while dihydroactinidiolide is an effective analeptic agent, the preferred analeptic agent, tetrahydroactinidiolide, restored respiration in a significantly greater (P .01) number of animals than the other ,analeptics.

I claim:

1. A process for treating respiratory depression which comprises administering parenternally to a mammalian host experiencing respiratory depression a pharmacologically eifective dose of a compound selected from the group consisting of 2-hydroxy-2,6,6-trimethylcyclohexylidene acetic acid, 'y-lactone and 2-hydroxy-2,6,6-trimethylcyclohexyl acetic acid, 'y-lactone.

2. The process of claim 1 wherein said compound is 2 hydroxy 2,6,6-trimethylcyclohexylidene acetic .acid, 7- lactone.

3. The process of claim 1 wherein said compound is 2-hydroxy-2,6,6-trimethylcyclohexyl acetic acid, -lactone.

ALBERT T. MEYERS, Primary Examiner S. J. FRIEDMAN, Assistant Examiner US, Cl. X.R. 260-3436 11/1961 Shavel et a1 260-343.6 

